Examples of panoramic periscopes of this type are described in GB-B-1,272,742, U.S. Pat. No. 3,464,757, U.S. Pat. No. 3,200,250, U.S. Pat. No. 3,549,231 and U.S. Pat. No. 4,108,551.
Depending on the type of use and configuration, the periscope may be provided with an optical path in the visible spectrum, or with an infrared optical path with an associated infrared sensor, or with a laser telemeter, or with a combination of these elements.
The space available in the vehicle where the periscope is installed is restricted and this results in the need for a compact structure. Arranging two or three optical paths (visible, infrared and laser) in a panoramic periscope is difficult since it requires a large amount of space.
Moreover, assembly of the various optical components is complex and delicate, since said components must be mounted and aligned with great precision. This is made difficult owing to the fact that the various components frequently have to be assembled and disassembled. It is required, moreover, to reduce the number of optical components in order to simplify the structure and increase the optical efficiency of the apparatus.
The general object of the present invention is to provide a periscope of the type mentioned above which overcomes the drawbacks of conventional periscopes. In particular, the object of the invention is to provide a periscope which is compact even when two or more optical paths are combined in it. It must also be easy and reliable as regards assembly and adjustment of all its components.
In some configurations of the periscope an infrared viewing module with an I.R. sensor is provided. At present, various types of arrangements of the infrared sensor, or so-called heat chamber, exist in panoramic periscopes. In particular, there exist solutions in which the entire heat chamber and the associated optics are arranged inside the central body of the periscope. This allows perfect alignment of the optics during assembly and avoids risks of misalignment. However, this solution has considerable drawbacks since the periscope body assumes notable proportions with consequent problems of installation and limitations as regards the possibility of combining, with the same periscope, an optical path in the visible spectrum.
When the periscope has a heat chamber for night-time viewing in the infrared range, the present invention has the object of providing a periscope in which joining of the heat chamber to the periscope body can be performed in a particularly simple manner and does not give rise to positioning and alignment problems and which, moreover, is particularly compact and easy to install.
In this context, a further particular object of the present invention is to provide a periscope of the type mentioned above, in which the optical elements along the path of the infrared beam are reduced, so that it is possible to have a more powerful signal.
In some periscopes, a laser telemeter is also provided. In this case a separator element inside the periscope body separates the laser path from the optical path in the visible and/or infrared range. A type of periscope currently known has a separator prism with a dichroic surface oriented so as to deviate the visible beam and allow the laser beam to pass through. The deviated visible beam is reflected onto a side surface of the prism and from here is redirected to a facing side surface from where it emerges so as to be directed towards the viewing module. This separator system has large dimensions and occupies a considerable amount of space inside the periscope body.
Within the scope of the general object of the present invention (i.e. of providing a periscope which is particularly compact and has a small number of optical elements), if the periscope has a laser path, a particular object is that of providing a periscope which has an element for separating the laser beam from the visible beam, which has a particularly limited height, so as to reduce the space occupied inside the periscope body and facilitate, where necessary, the arrangement inside the said periscope body of optics for viewing in the infrared range.
In this context, a further object of the present invention is to provide a periscope in which the separator element allows formation of a visible-beam path, which is more favourable from the point of view of the layout of the device.
Normally the rotating head-piece is mounted on the periscope body by means of a system of supports. The volume of the head-piece is delimited at the bottom by a sealed window, which is transparent for a certain radiation range, for example visible radiation and infrared radiation, so as to allow daytime and nighttime viewing. The volume of the central body of the device is in turn closed by a sealed window which is transparent for the same radiation range. Assembly is performed by arranging the two windows facing one another. This therefore results in isolation of the internal volumes of the head-piece and central body from the outside, while the radiation which penetrates into the central body so as to allow viewing directly or via an infrared sensor passes through at least two separation windows.
This has been considered necessary in particular in periscopes with at least two optical paths, because these devices are required to operate in critical environmental conditions and it is necessary to ensure complete isolation, from the outside, of the delicate optical instruments contained in the device. Moreover, the sealing action with respect to the exterior must be ensured so as to prevent escaping of the gas forming the controlled atmosphere inside the device.
However, the presence of two separation windows between the volume of the head-piece and the volume of the body of the device constitutes a serious drawback since it greatly reduces the energy of the beam which reaches the viewing means. This drawback is accentuated in the case of periscopes intended for night-time viewing, since the signal in the infrared range is per se very weak. A loss of signal due to absorption by the two windows constitutes an extremely negative factor in terms of efficiency of the device.
When the periscope must be used for both night-time viewing (by means of infrared images) and daytime viewing (in the visible range) it is necessary to choose a material which is transparent both for radiation in the far infrared range and for visible radiation. The multi-spectral material which can be used in such a wide range of the spectrum reduces the viewing clarity in the visible range, imposing considerable limitations on the overall thickness of the windows.
Moreover, in conventional periscopes, often part of the body of the device is mounted on the vehicle from the inside. If the device is subject to frequent assembly and disassembly operations for reasons of technical maintenance and verification, there is the risk of axial and angular misalignment of the head-piece and body. Such misalignment must be avoided at all costs since, if a sighting grid is provided inside the body of the device, this grid must always be perfectly aligned with the axis of the beam coming from the head-piece. If this condition is not maintained, the device, used for aiming weapons and the like, loses its operational efficiency or the latter is seriously impaired.
In order to avoid these drawbacks, it is necessary to observe very precise tolerances as regards the surfaces for joining together the head-piece and body of the device, with an obvious negative effect in terms of cost.
One particular object of the present invention is to provide a device which allows the signal losses to be reduced, in particular in the far infrared range.
One further particular object of the present invention is to provide a device which eliminates the need for disassembling the head-piece from the body and which therefore eliminates the risk of misalignment between the optics contained in the body and the optics contained in the head-piece, and in particular the misalignment between the sighting grid and the optics of the rotating panoramic head-piece.
A further object of a particular embodiment of the present invention is to provide a device which does not require excessively small machining tolerances as regards the surfaces for joining together the head-piece and body of the device.
Yet another object of an embodiment is that of obtaining a high degree of integration between the components and functions, so as to assemble everything within the space contained in a cylinder and allow assembly of the device from above.
In periscopes of the type currently known, which are provided with an optical path in the visible spectrum for daytime viewing, complex systems for varying the magnification ratio are used. These systems comprise an arrangement of movable optics which change condition depending on the magnification ratio required.
The known devices are costly and delicate, as well as being bulky, a feature which is a particularly unfavourable aspect when the periscope must be installed on vehicles where there are problems of space and robustness, as in the case of tanks used in armed combat.
When the periscope is provided with an optical path in the visible spectrum, a particular object of the present invention is to provide a periscope having a system for changing the magnification ratio which is simpler, more reliable and less bulky than conventional systems.